In U.S. Pat. No. 3,988,710, entitled "Contactless Linear Rotary Potentiometer", filed in the name of Edward Frank Sidor and Frank B. Desio and assigned to the assignee of the present invention, a device was disclosed in which a rotary shaft was coupled to a rotor that carried a permanent magnet which was formed in the shape of a portion of a circle, and a pair of elongated, hollow magnetically saturable, tubular sensing elements were positioned adjacent the rotor. The sensing elements each had at least one drive winding threaded through them and they were positioned with their axes aligned at an acute angle and were inserted into slots in a spacer that was positioned directly below the rotor that carried the magnet. A very linear contactless potentiometer was thus achieved with the initial position of the potentiometer being set so that the straight edges of the magnet werre initially positioned normal to the elongated axes of the two hollow sensing elements.
The device of the present invention is an entirely different type of device in that it functions as a contactless switch wherein the change of saturation state of the magnetic sensing elements from a saturated to a nonsaturated condition is a rapid one as the permanent magnet is displaced slightly from its initial position, and not a linear gradually changing condition such as occured in the prior Sidor et al patent. The version that is shown in FIGS. 1 and 2 is presently preferred since the switching mechanism of the present invention can be implemented by using the same basic components as that shown in the prior Sidor et al patent, with the exception of the spacer that is below the rotor which is provided with slots that are aligned so that the acute angle that is formed by the elongated axes of the sensing elements faces in the opposite direction than it did in the Sidor et al patent.
By this simple modification, the embodiment of FIGS. 1 and 2 provides an entirely different type of sensing device since the straight edges of the permanent magnet of the present invention are initially aligned substantially along the elongated axes of the sensing elements and not normal to them as in the prior Sidor et al patent. Thus, instead of a very linear change of output signal from the sensing elements with respect to the position of the rotor, a very rapid change in output signal is obtained, as illustrated in FIG. 3, thereby providing the contactless switching action.